Previous research has noted that children display different patterns of acquisition when learning color and size terms. This project proposes that the different patterns of acquisition observed for different dimensional adjectives is a product of the way that the different dimensions are presented and talked about in the input to children-- ways that highlight comparison or ways that highlight categorization. This proposal seeks to address a gap in our understanding of how parents talk about dimensions to children and to relate children's understanding of dimension terms to the ways that dimensions are talked about in the adult input. The specific questions addressed are: (1) How do parents typically talk about dimension terms? (2) Which contexts elicit comments about specific dimensions and which elicit comparison versus categorization? (3) Does the structure of adult input predict children's pattern of acquisition for specific dimension terms? (4) How does the way parents structure the input relate to children's understanding of dimension terms and how does children's understanding of dimension terms relate to how parents structure the input? (5) Can changing the way that dimensions are talked about alter the course of acquisition for learning dimension terms? These questions are addressed by observing parents talking about dimension with their children and measuring children's comprehension of specific dimensions both longitudinally and cross-sectionally, longitudinally tracking children's acquisition of dimension terms, and a dimension term training study.